2008-04-15_REVISION - M1980244 (197)

Home Browse Search

WHEXSIopeEvaluation AdrianBrown Table 7. Point Load Test Results Volcanics (phonolite, breccia) 13,700 psi 94 mPa Granites (granite, schist, gneiss) 13,200 psi 91 mPa As can be seen, the average intact rock strength of both rock types are indistinguishable; approximately 13,500 psi or 92 mPa. 3.2.2 Uniaxial compression testing Uniaxial compression testing has been previously performed on 56 samples of Diatremal volcanic rocks from the Main Cresson Mine (Brown, 1997). In this program, a total of 31 UCS tests have been reported to date, of which the average failure strength was 7,952 psi (54 mPa). Of these tests, 12 failed through intact rock, and displayed an average UCS of 11,765 psi (81 mPa). Table 2. Uniaxial Compressive Strength Test Results Volcanics honolite, breccia 13,600 si 94 MPa Granites anite, schist, eiss 11,765 si 81 MPa • The UCS test is prone to failure along foliation, which is the likely explanation of the lower results for this test when compazed with the point load test (where the results are ignored if the material fails along a foliation plane). 3.2.3 Hoek-Brown m~ testina Compressive Strength exhibited by intact rocks is affected by confining stress. The relationship between failure stress and confining stress is given by (Hoek, 2001): s1,=s~,+mis3, where: s 1' =major principal effective stress at failure s 3' =minor (confining) principal effective stress at failure s ~; =Unconfined Compressive Strength (UCS) of intact rock m; = Hoek-Brown parameter The diatremal volcanic rocks have been previously tested for this parameter by staged triaxial testing on samples of the same rock (Itasca, 1999). As part of the WHEX program, two tests have been performed on the granitic rocks. The results are presented in Table 3. Table 3. Hoek-Brown m, Test Results Volcanics honolite, breccia 8.7 Granites 'te schist, eiss 9.5 • Report 1385L.200309017 5